Since laser beam has advantages of good collimation, high power and high light intensity, laser beam generating apparatuses have a wide range of application in modern industry. Taking a manufacturing application of a laser light source on touch panel in electronic industry as an example, through laser modification, crystallinity of indium-tin oxide (ITO) of local area can be enhanced, by which chemical resistance, weatherability and resistance stability of ITO thin film can be enhanced, so as to improve product quality, and the laser light source can also be applied to a laser lift off (LLO) technique of an organic light emitting device (OLED) or a laser annealing process of an insulated-gate bipolar transistor (IGBT).
However, since the laser beam emitted by the laser light source has high coherence, when the laser beam irradiates an unsmooth object surface (for example, a lens or a reflector, etc. having surface microstructures), the laser beam from the object surface has an interference to produce speckles on the irradiation surface. The speckles are irregular noise-like patterns (for example, irregular bright and dark stray dots), which may lead to uneven illumination on the irradiation surface, and cause reduction of optical quality of a device using the laser light source.